For some elements, use of toenail levels as a surrogate measure of exposure may provide an estimate of exposure superior to that made on the basis of data from food frequency questionnaires, hair, blood levels, or other measures. We hypothesize that this is the case for a group of elements (Ca, Mg, Fe, Zn, Cu, Mn, Se, Mo, Cr, Co, Hg, and Al), that has a purported link with chronic disease. Improved methods of assessing exposure to these elements will facilitate studies of their adverse or beneficial health effects. Repeated samples of whole-diet homogenates and toenails were collected over a one-year period from 77 subjects. The element content of diet and toenail specimens is being determined by neutron activation analysis and graphite furnace atomic absorption. After the concentration of the trace elements in the toenails and diet specimens has been determined, we will examine how well the toenail level of each element reflects intake.